JPH0939453A - Thermal magnetic recording medium - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a thermal magnetic recording medium having excellent conservation property, particularly excellent preservative property under high temperature and humidity, while excellent thermal recording property and magnetic recording property usable also as a rolled paper and cards are maintained. SOLUTION: In a thermal magnetic recording medium having at least a magnetic recording layer, a masking layer, a thermal recording layer, and a protective layer layered in sequence on a base body, an anchor layer having, as a main component, at least one kind of resin to be selected from a nitrocellulose resin and an acrylic resin is provided in between the magnetic recording layer and the masking layer. The thermal recording layer contains a leuco dye and a developer which are substantially insoluble in an aromatic hydrocarbon solvent and a resin soluble in the aromatic hydrocarbon solvent as main components.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat-sensitive magnetic recording medium having good recording characteristics and excellent storage stability, and particularly to tickets such as boarding tickets, commuter tickets, pass tickets, and prepaid cards. The present invention relates to a thermosensitive magnetic recording medium which can be applied.

[0002]

2. Description of the Related Art The heat-sensitive recording system is widely used in facsimiles and printers because it has the advantages that the apparatus can be made compact and lightweight, recording can be performed without noise, and consumables such as developer and transfer paper are unnecessary. In addition to being used for the output of the above, it has been extensively applied in recent years to ticket papers such as train tickets, commuter tickets, pass tickets, cards such as prepaid cards, and labels such as POS labels. In particular, there are many examples of combination with a magnetic recording system for ticket papers and cards. The recording medium used in the thermal recording system is Japanese Patent Publication No.
As described in Japanese Patent No. 14035, a so-called "NCR type" is widely used in which a colorless or light-colored leuco dye and a color developer, which is an acidic substance, are used as coloring components. Such recording media include leuco dyes such as fluoranes, fluorenephthalides, divinylphthalides, phenothiazines, auramines, spiropyrans, rhodamine lactams, including triarylmethane phthalides such as crystal violet lactone. And a developer such as bisphenol A such as phenols, thiobisphenols, naphthols, benzoic acid, salicylic acid, gallic acid, etc., dispersed in an aqueous binder such as polyvinyl alcohol. The heat-sensitive recording layer is formed on the substrate. This type of heat-sensitive recording medium has excellent features such as clear recording, high heat sensitivity, and white background. However, this type of thermal recording medium contains D contained in the vinyl chloride film.
By contact with plasticizers such as OP and chemicals such as alcohols,
In addition to chemical resistance problems such as decolorization of recorded areas and color development of unrecorded areas, there is basically a problem with water resistance that the thermosensitive recording layer softens or elutes and loses when it comes into contact with water. It was something that had.

In particular, when this type of heat-sensitive recording medium is used for ticket papers and cards such as passenger tickets and commuter tickets, not only recording characteristics but also severe quality characteristics, that is, environmental resistance characteristics are strongly required. That is, with respect to a paper sheet used for a long period of time such as a commuter pass, severe chemical resistance and water resistance are required without decoloring of a recorded portion and coloring of an unrecorded portion as described above. In order to solve these various characteristics under such strict requirements, for example, in Japanese Patent Publication No. 3-26154, in order to form a heat-sensitive recording layer using an aromatic hydrocarbon solvent as a solvent,
Uses a leuco dye and a developer that are substantially insoluble in aromatic hydrocarbon solvents, and uses polymethylmethacrylate resin, polyethylmethacrylate resin, and polybutylmethacrylate resin soluble in aromatic hydrocarbon solvents as a binder. Ink compositions for thermal recording media have been proposed. Also,
JP-A-56-126193, JP-A-57-29491
JP-A-56-146794 and the like describe a heat-sensitive recording material in which a specific surface layer is provided on the heat-sensitive recording layer to improve chemical resistance and water resistance.

On the other hand, a conventional heat-sensitive magnetic recording medium in which the above-mentioned heat-sensitive recording material having improved chemical resistance and water resistance is combined with a magnetic recording medium is a magnetic recording layer and a concealing layer containing aluminum powder on a support. It has been proposed that a thermosensitive recording layer and a protective layer are sequentially laminated. However, the conventional thermosensitive magnetic recording medium is resistant to the effects of the components such as the dispersant contained in the magnetic recording layer, the fatty acid remaining in the aluminum powder used for masking the coloring, and the high boiling point solvent. It had a big problem in environmental preservation. In particular, the problem is that the heat-sensitive recorded image is erased in the high-temperature and high-humidity atmosphere, the background fog on the heat-sensitive recording layer occurs, and the recording characteristics are poor when re-recording after being left in the high-temperature and high-humidity atmosphere It was something that had. Furthermore, the adhesion between the hiding layer and the magnetic recording layer and the heat-sensitive recording layer is poor, and there is a problem that peeling occurs.

[0005]

DISCLOSURE OF THE INVENTION The present invention is intended to improve the above-mentioned problems and, specifically, has good chemical resistance and water resistance that can be used as ticket papers and cards. The present invention provides a thermosensitive magnetic recording medium which, while being maintained, has excellent environmental resistance storage stability, particularly good storage stability under high temperature and high humidity conditions.

[0006]

The present invention relates to a thermosensitive magnetic recording medium in which at least a magnetic recording layer, a concealing layer, a thermosensitive recording layer, and a protective layer are sequentially laminated on a substrate, and a nitro layer is provided between the magnetic recording layer and the concealing layer. An anchor layer containing at least one resin selected from cellulose resins and acrylic resins as a main component is provided, and the heat-sensitive recording layer is substantially insoluble in an aromatic hydrocarbon solvent, a leuco dye and a developer, and aromatic carbonization. A thermosensitive magnetic recording medium characterized by containing a resin soluble in a hydrogen solvent as a main component.

Next, materials constituting the thermosensitive magnetic recording medium of the present invention will be described. The substrate has a thickness of 150 μm
A non-magnetic material such as a 1 mm polyester film, a vinyl chloride resin film, synthetic paper, wood pulp paper or laminated paper can be applied. Practically, plastic films and synthetic papers are suitable. As the magnetic material used for the magnetic recording layer, magnetic powder such as γ-iron oxide, cobalt-doped γ-iron oxide, chromium oxide, barium ferrite, and strontium ferrite is applied. These magnetic materials are dispersed in a binder such as vinyl chloride / vinyl acetate copolymer, vinyl chloride / vinyl acetate / vinyl alcohol copolymer, polyurethane resin, polyester resin, epoxy resin, etc. together with other additives such as pigments. A magnetic recording layer is formed by forming a magnetic paint or ink, coating or printing this on a substrate, and then drying. At this time, a magnetic field orientation treatment may be performed before the magnetic recording layer is dried.

The anchor layer is formed mainly of one or more resins selected from nitrocellulose resins and acrylic resins. Such a nitrocellulose resin is one in which three hydroxyl groups in the glucose residue of cellulose are substituted with nitro groups, and the nitrogen amount as the degree of substitution is 10.0 to 1
2.5% and a degree of polymerization of about 500 to 1000 are applied. Among them, those having a nitrogen content of 11.5 to 12.2% are particularly preferable from the viewpoints of film-forming property, pigment dispersibility, paint property, solvent solubility and the like.

As the acrylic resin, homopolymers, copolymers of various acrylic monomers and copolymers with other vinyl monomers are appropriately used. Specifically, acrylic acid, methacrylic acid, methyl acrylate, ethyl acrylate, n-butyl acrylate, 2-ethylhexyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, n-butyl methacrylate, methacrylic acid Acid n-octyl, 2-ethylhexyl methacrylate,
Homopolymers of acrylic monomers such as phenyl methacrylate, acrylonitrile, and acrylamide, copolymers thereof, and these acrylic monomers and styrenes such as styrene, methylstyrene, ethylstyrene, n-butylstyrene, and chlorostyrene. Type, vinyl chloride,
Examples thereof include copolymers with other vinyl monomers such as vinyl acetate and vinyl alcohol.

In the present invention, when an acrylic resin is used for the anchor layer, it is preferable that an acrylic copolymer curable with an isocyanate or aziridine curing agent is blended with the curing agent. Such an acrylic copolymer has at least an acrylic monomer having a functional group such as —COOH, —OH, and —NH _{2 described} below as a copolymerization component, and is copolymerized with an acrylic monomer or a vinyl monomer as described above. It is united. Examples of the acrylic monomer having such a functional group include acrylic organic acids such as acrylic acid, methacrylic acid, icotanic acid and maleic acid, hydroxyethyl (meth) acrylate, (meth) acrylic acid.
Hydroxyalkyl esters of (meth) acrylic acid such as 2-hydroxyethyl acrylate, 2-hydroxypropyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, aminoethyl (meth) acrylate, (meth) acrylic Examples thereof include (meth) acrylic acid aminoalkyl esters such as 2-aminoethyl acid, 2-aminopropyl (meth) acrylate, and 2-aminobutyl (meth) acrylate, and acrylic acid amides, but are not limited thereto. Not something. Among the acrylic copolymers as described above, an acrylic copolymer having at least either an acid value of 10 or more or an OH value of 20 or more in terms of solid content is preferable. Further, considering the surface strength and adhesiveness of the coating film, the glass transition temperature is preferably at least 50 ° C. or higher.

In the present invention, it is preferable to use an isocyanate type or aziridine type curing agent in order to cross-link the acrylic type copolymer having the above functional group. As the isocyanate-based curing agent, those having at least two isocyanate groups in the molecule are appropriately used, and examples thereof include tolylene diisocyanate, 1,5-naphthalene diisocyanate, triphenylmethane triisocyanate, xylene diisocyanate, hexamethylene diisocyanate and dichlorohexyl. Examples include methane diisocyanate and modified products thereof. Specifically, a coronate-based curing agent (manufactured by Nippon Polyurethane Company) or a dismodular-based curing agent (manufactured by Bayer) can be used. Examples of the aziridine-based curing agent include trimethylolpropane-tri-β-aziridinylpropionate, tetramethylolmethane-tri-β-aziridinylpropionate, N, N′-diphenylmethane-4,4. -Bis (1-aziridinecarboxamide), N, N'-hexamethylene-1,6-bis (1-
Aziridine carboxamide) and the like.

According to the present invention, by using the resin as described above for the anchor layer, good storability can be obtained without decoloring of the heat-sensitive recorded image and generation of background fog in the heat-sensitive recording layer when left in a high temperature and high humidity atmosphere. To be This is because the components such as the dispersant remaining in the magnetic recording layer and the residual fatty acid or high boiling point solvent used as a dispersion aid in the manufacturing process of the scaly aluminum powder exude to the surface of the concealing layer. Is supposed to be prevented. Further, by providing such an anchor layer, penetration of the subsequently formed hiding layer coating material into the magnetic recording layer is prevented, so that not only the surface coating property of the hiding layer is improved but also the surface smoothness is improved. Therefore, the adhesion between the concealing layer and the heat-sensitive recording layer that is subsequently formed is also improved, and good physical strength is achieved without problems such as peeling. The anchor layer can be formed from a solution containing the above resin as a main component by a conventional coating method or printing method, and the layer thickness is 0.5 to 5 μm, preferably 1 to 3 μm.
m.

As the concealing layer, various pigments having a function of concealing coloring of the magnetic recording layer are dispersed in a binder. As the pigment used in the hiding layer, aluminum powder, metal powder such as silver powder, carbon black, titanium oxide, calcium carbonate, aluminum hydroxide, silica,
Inorganic and organic pigments such as talc and polyethylene powder are mentioned. In the present invention, among these pigments, aluminum powder is preferably used in terms of its hiding property and appearance color tone. As such aluminum powder, a scaly powder having an average particle diameter of 5 to 20 μm is generally used.

As the binder for the concealing layer, nitrocellulose resin, acrylic resin, vinyl chloride / vinyl acetate copolymer, vinyl chloride / vinyl acetate / vinyl alcohol copolymer, polyester resin, etc. are used. It is preferable to use a resin having a good powder dispersibility. The mixing ratio of the aluminum powder and the resin used as the binder in the concealing layer is preferably 2: 8 to 7: 3, and particularly preferably 4: 6 to 6: 4. The hiding layer is
It can be formed by a conventional coating method or printing method using a solution in which aluminum powder is dispersed in a resin containing the above-mentioned resin as a main component, and the layer thickness thereof is in the range of 0.5 to 5 μm, preferably 1 to It is 3 μm.

The leuco dye contained in the heat-sensitive recording layer of the present invention and the color developing agent which develops the color of the leuco dye when heated are
Both are used that do not substantially dissolve in the aromatic hydrocarbon solvent. This is because if either the leuco dye or the color developer is dissolved in the solvent, the heat-sensitive recording layer itself becomes colored and cannot be used at all. Examples of specific compounds of the leuco dye that can be used in the present invention are shown below as structural formulas (1) to (5), but the present invention is not limited thereto.

Embedded image

Specific examples of the color developer usable in the present invention are shown below as structural formulas (6) to (15), but the invention is not limited thereto.

Embedded image These leuco dyes and color developers may be used alone or in admixture of two or more in order to adjust the color tone and thermal sensitivity.

As the binder for the heat-sensitive recording layer in the present invention, a resin soluble in an aromatic hydrocarbon solvent is used. The aromatic hydrocarbon solvent referred to here is one that does not substantially dissolve the leuco dye and the developer used in the present invention, but only the binder, and specifically, benzene and toluene. , Xylene, mesitylene and the like. Examples of such a binder soluble in an aromatic hydrocarbon solvent include styrenes such as styrene, methylstyrene, ethylstyrene, n-butylstyrene, and chlorostyrene, methyl acrylate, ethyl acrylate, and acrylic acid n. -Butyl, 2-ethylhexyl acrylate, phenyl acrylate, methyl methacrylate, ethyl methacrylate, n methacrylate
-Butyl, n-octyl methacrylate, methacrylic acid 2
Examples thereof include, but are not limited to, homopolymers and copolymers of acrylic acid derivatives (monomers A) such as ethylhexyl and phenyl methacrylate.

In the present invention, the resin as the binder of the heat-sensitive recording layer preferably contains an acrylic copolymer curable with an isocyanate or aziridine curing agent together with the curing agent. Examples of such an acrylic copolymer include the above-mentioned monomer A and the following -COOH,
Examples thereof include a copolymer with an acrylic monomer (monomer B) having a functional group such as —OH and —NH ₂ . Examples of the monomer B include acrylic organic acids such as acrylic acid, methacrylic acid, icotanic acid and maleic acid,
(Meth) acrylic acid hydroxyalkyl esters such as hydroxyethyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, 2-hydroxypropyl (meth) acrylate, and 2-hydroxybutyl (meth) acrylate; (Meth) acrylic acid aminoalkyl esters such as aminoethyl (meth) acrylate, 2-aminoethyl (meth) acrylate, 2-aminopropyl (meth) acrylate, and 2-aminobutyl (meth) acrylate, acrylic acid Examples include, but are not limited to, amides. In the present invention, the acrylic copolymer may be a copolymer of an acrylic monomer (monomer B) having a functional group as described above and a vinyl monomer other than the monomer A. As other vinyl monomers,
Examples thereof include acrylonitrile, vinyl chloride, vinylidene chloride, vinyl acetate and the like, but are not limited thereto. Among the acrylic copolymers as described above,
An acrylic copolymer having an acid value of 10 or more or an OH value of 20 or more in terms of solid content is preferable. Further, considering the surface strength and adhesiveness of the coating film, the glass transition temperature is preferably at least 50 ° C. or higher.

In the present invention, it is preferable to use an isocyanate-based or aziridine-based curing agent as a curing agent for crosslinking the acrylic copolymer having a functional group as described above. As a specific example of the isocyanate-based or aziridin-based curing agent, the same curing agent used in the anchor layer can be applied.

The heat-sensitive recording layer of the present invention is a heat-sensitive recording layer obtained by dissolving the above-mentioned binder in an aromatic hydrocarbon solvent and further dispersing the leuco dye and the developer in the solution. It is formed by applying and drying a paint on the hiding layer. The compounding ratio of the leuco dye and the color developer is 10: 1 to
It is 1:10, preferably 1: 1 to 1: 3, and the ratio of the binder in the thermosensitive recording layer is 5 to 95 by weight in terms of solid content.
%, Preferably 15 to 50%.

If desired, additives can be added to the heat-sensitive recording layer of the present invention. Examples of the additives include inorganic pigments such as aluminum hydroxide, calcium carbonate, silica, and talc, organic pigments such as polyolefin resin, polyethylene resin, urea-formalin resin, metal salts of higher fatty acids, waxes, and lubricants such as fluorocarbons. , UV absorbers and the like. Further, it is possible to use various sensitizers as long as the heat resistance is not impaired. The method for forming the heat-sensitive recording layer may be a conventional coating method or printing method,
The layer thickness is 1 to 8 μm, preferably 2 to 5 μm. The thermosensitive magnetic recording medium of the present invention has excellent chemical resistance and water resistance obtained by providing the thermosensitive recording layer as described above, and has excellent environmental resistance, particularly high temperature and high temperature, in combination with the effect of the anchor layer. Good storability in a moist atmosphere is achieved.

In the present invention, the protective layer provided on the heat-sensitive recording layer is mainly composed of a resin having excellent chemical resistance and good film-forming property, and the background of the heat-sensitive recording layer by contact with oils, solvents, water and the like. It has the function of improving the abrasion resistance when it is used as, for example, a ticket or a card, as well as a barrier effect for preventing color development and erasing of the recorded portion. As the resin used for the protective layer, a water-soluble resin, a water-dispersible resin, a solvent-based resin or the like can be appropriately selected and used, and among them, an ultraviolet ray or electron beam curable resin is excellent in chemical resistance and strong. It is preferable because it has abrasion resistance. As the UV or electron beam curable resin, for example, those capable of performing radical polymerization of monomers and oligomers containing a vinyl group, specifically, many types such as oligo acrylate, urethane acrylate and silicon acrylate are applied. it can. When it is cured by ultraviolet rays, it is necessary to include a photopolymerization initiator such as benzoylalkyl ether, benzophenone, benzyl Michler's ketone. Further, an epoxy compound which undergoes ring-opening polymerization by a cationic reaction with a Lewis acid catalyst can also be used as an ultraviolet curable resin, in which case an aromatic halonium salt of Lewis acid, an aromatic sulfonium salt of Lewis acid or the like is used as a photopolymerization initiator. is necessary.

Since the protective layer is in direct contact with the thermal head,
When printing, it may be exposed to high temperatures of 300 ° C or higher.
One or more selected from pigments, higher fatty acids or metal salts thereof, heat-fusible lubricants, and lubricants are added for the purpose of improving matching with the thermal head. Examples of the pigment include organic pigments such as aluminum hydroxide, silica, talc, and urea-formaldehyde resin, or inorganic pigments. As the heat-fusible lubricant, polyethylene wax, paraffin wax, fluorocarbon or the like is used. As the lubricant, liquid lubricants such as paraffin and silicone oil, and solid lubricants such as reactive silicone resin are used. The amount of pigment, higher fatty acid or metal salt thereof, heat-fusible lubricant, lubricant added is 1 to 40 parts by weight, preferably 3 to 100 parts by weight with respect to 100 parts by weight of the ultraviolet or electron beam curable resin.
30 parts by weight. If the addition amount is less than this, the matching property with the thermal head is not sufficiently improved. The method for forming the protective layer may be a conventional coating method or printing method,
The layer thickness is in the range of 0.1 to 3 μm, preferably 0.5 to 2 μm.
m.

[0024]

【Example】

Example 1 A coating material for the magnetic recording layer was prepared with the following composition.・ 100 parts by weight of barium ferrite (MC127 manufactured by Toda Kogyo Co., Ltd.) ・ 3 parts by weight of carbon black (MA100 manufactured by Mitsubishi Chemical Co., Ltd.) ・ 20 parts by weight of vinyl chloride / vinyl acetate / vinyl alcohol copolymer (S-REC A by Sekisui Chemical Co., Ltd.) Polyurethane resin (N2304 manufactured by Nippon Polyurethane Co., Ltd.) 20 parts by weight Toluene 60 parts by weight Methyl ethyl ketone 60 parts by weight Methyl isobutyl ketone 60 parts by weight After dispersing the above mixture in a ball mill for 8 hours, polyisocyanate resin (manufactured by Nippon Polyurethane Co., Ltd.) 5 parts by weight of Coronate L) was added to prepare a magnetic paint, and the thickness was 188
A magnetic recording layer was formed by applying a gravure coating method on a substrate made of a white polyethylene terephthalate film having a thickness of .mu.m, performing magnetic field orientation treatment, and then drying. The dry coating amount was 30 g / m ² .

An anchor layer coating material having the following composition was applied onto the obtained magnetic recording layer by a gravure coating method and dried to form an anchor layer. The dry coating amount was 2 g / m ² . -Nitrocellulose resin (Celnova BT-SL manufactured by Asahi Kasei Co., Ltd.) 20 parts by weight-Toluene 40 parts by weight-Methyl ethyl ketone 40 parts by weight Next, a coating for a masking layer having the following composition is applied on the anchor layer by a gravure coating method and dried to mask. Layers were formed. The dry coating amount was 3 g / m ² . -Aluminum paste (MR9000 manufactured by Asahi Kasei) 40 parts by weight-Acrylic polyol resin (LR582 manufactured by Mitsubishi Rayon Co., Ltd.) 50 parts by weight-Isocyanate curing agent (NY218A manufactured by Mitsubishi Chemical Co.) 5 parts by weight-Toluene 150 parts by weight-Methyl ethyl ketone 150 parts by weight Department

Next, a heat-sensitive recording layer coating material having the following composition was prepared on the concealing layer, and the coating material was dried to form a heat-sensitive recording layer. The dry coating amount was 5 g / m ² . 10 parts by weight of a toluene dispersion of the leuco dye of the structural formula (5) (solid content 20% by weight) 15 parts by weight of a toluene dispersion of the developer of the structural formula (6) (20% by weight solid content) Toluene dispersion of aluminum hydroxide (solid content 30% by weight) 10 parts by weight Toluene solution of styrene / methacrylic acid / hydroxyethyl acrylate copolymer (solid content 20% by weight, acid value 6.5, OH value 65) 15 parts by weight ・ Aziridine-based curing agent (trimethylolpropane-tri-β-aziridinylpropionate) 0.4 parts by weight Next, a mixture having the following composition was prepared as a protective layer and UV offset method was applied on the heat-sensitive recording layer. Was printed and UV-cured to form a protective layer having a thickness of 1 μm, and the thermosensitive magnetic recording medium of the present invention was produced. -Polyester acrylate (San Nopco Photomer 5018) 100 parts by weight-1- (4'-dodecylphenyl) -2-hydroxy-2-methylpropan-1-one 1 part by weight

Example 2 A thermosensitive magnetic recording medium of the present invention was produced in the same manner as in Example 1 except that the paint for the anchor layer having the following composition was used. -Acrylic polyol resin (Mitsubishi Rayon LR582) 50 parts by weight-Isocyanate curing agent (Mitsubishi Chemical NY218A) 5 parts-Toluene 100 parts by weight

Example 3 A thermosensitive magnetic recording medium of Example 3 was prepared in the same manner as in Example 1 except that the coating composition for the hiding layer used in Example 1 was the one having the following composition. -Aluminum paste (MR9000 manufactured by Asahi Kasei) 40 parts by weight-Polyester resin (Vylon 200 manufactured by Toyobo Co., Ltd.) 60 parts by weight-Toluene 150 parts by weight-Methyl ethyl ketone 150 parts by weight

Comparative Example 1 Example 1 except that the anchor layer is not provided in Example 1.
A thermosensitive magnetic recording medium for comparison was prepared in the same manner as in. Comparative Example 2 Example 3 except that the anchor layer is not provided in Example 3.
A thermosensitive magnetic recording medium for comparison was prepared in the same manner as in. Comparative Example 3 A thermosensitive magnetic recording medium for comparison was prepared in the same manner as in Example 1 except that the anchor layer was provided between the hiding layer and the heat sensitive recording layer instead of between the magnetic recording layer and the hiding layer. .

Comparative Example 4 A thermosensitive magnetic recording medium for comparison was prepared in the same manner as in Example 1 except that the coating material having the following composition was used as the coating material for the anchor layer. -Polyester resin (Vylon 200 manufactured by Toyobo Co., Ltd.) 20 parts by weight-Isocyanate curing agent (Coronate L manufactured by Nippon Urethane Co., Ltd.) 5 parts by weight-Toluene 50 parts by weight-Methyl ethyl ketone 50 parts by weight

Comparative Example 5 A comparative thermosensitive magnetic recording medium was prepared in the same manner as in Example 1 except that the paint for the anchor layer used in Example 1 had the following composition. -Polyurethane resin (N2301 manufactured by Nippon Polyurethane Company) 20 parts by weight-Isocyanate curing agent (Coronate L manufactured by Nippon Polyurethane Company) 5 parts by weight-Toluene 50 parts by weight-Methyl ethyl ketone 50 parts by weight

Comparative Example 6 A comparative thermosensitive magnetic recording medium was prepared in the same manner as in Example 1 except that the paint having the following composition was used as the paint for the thermosensitive recording layer.・ Aqueous dispersion of leuco dye of structural formula (5) (solid content 20% by weight) 10 parts by weight ・ Aqueous dispersion of developer of structural formula (6) (solid content 20% by weight) 15 parts by weight ・ Hydroxylation Aqueous dispersion of aluminum (solid content: 30% by weight) 10 parts by weight Acrylic emulsion (Movinyl 730 manufactured by Hoechst Synthetic Co., Ltd.) 20 parts by weight

The following characteristics of the thermosensitive magnetic recording media prepared in Examples 1 to 3 and Comparative Examples 1 to 6 were evaluated. (1) Adhesiveness Cellotape was attached to the printed surface and the state when strongly peeled off was observed. ○ No change at all × Peeling occurred at the interface between the hiding layer and the heat-sensitive recording layer or magnetic recording layer (2) Heat-sensitive recording characteristics 0.45 W using a line dot type thin film heat-sensitive head
An image was recorded at an energy of (1.0 mj / dot), and the solid black portion was measured with a visual filter of a Macbeth densitometer. (3) Environment-resistant storage property The heat-sensitive magnetic recording medium on which printing was recorded was left for 48 hours under the environmental conditions of temperature 55 ° C. and humidity 90% RH, and then the image density of the solid black portion and the background portion was measured. Further, the heat-sensitive recording characteristics were evaluated again on the background portion of the heat-sensitive magnetic recording medium after being left at the above high temperature and humidity, and the image density of the rerecorded portion was measured.

The results are shown in Table 1. It was confirmed that all the thermosensitive magnetic recording media of the present invention maintained good recording characteristics and had a strong laminated structure and excellent environmental storage stability. On the other hand, Comparative Examples 1 and 2 are inferior in environmental preservation resistance because no anchor layer is provided. In addition, Comparative Example 1 has poor adhesion, and Comparative Example 3 has an anchor layer as a hiding layer and a heat-sensitive recording layer. Since it was provided between the two, there was a problem of adhesion. Moreover, since Comparative Examples 4 and 5 are anchor layers containing a polyester resin or a polyurethane resin as a main component, good environmental preservation resistance cannot be obtained, and Comparative Example 6 uses a general aqueous binder. Due to the heat-sensitive recording layer, good water resistance was not obtained, and there were problems of adhesion and environmental preservation resistance. Regarding the magnetic recording characteristics, when recording was performed by the FM system with a recording density of 200 bpi using a magnetic head capable of recording and erasing on a magnetic layer having a coercive force of up to 3000 Oersted, normal recording and reproduction were possible. That is, there was no problem in magnetic recording characteristics.

[Table 1]

[0035]

The thermosensitive magnetic recording medium of the present invention comprises an anchor layer mainly composed of at least one resin selected from nitrocellulose resin and acrylic resin,
Since it has a structure in which a concealing layer and a heat-sensitive recording layer using a resin soluble in an aromatic hydrocarbon solvent as a binder are sequentially laminated, a remarkable effect of having unprecedented excellent environmental storage stability is exhibited. It is what is done.

Claims (3)

[Claims] 1. A thermosensitive magnetic recording medium in which at least a magnetic recording layer, a concealing layer, a thermosensitive recording layer, and a protective layer are sequentially laminated on a substrate, and is selected from a nitrocellulose resin and an acrylic resin between the magnetic recording layer and the concealing layer. An anchor layer containing at least one resin as a main component is provided, and the heat-sensitive recording layer contains a leuco dye and a developer that are substantially insoluble in an aromatic hydrocarbon solvent, and a resin soluble in an aromatic hydrocarbon solvent. A thermosensitive magnetic recording medium characterized by containing as a main component. 2. A thermosensitive recording layer containing an isocyanate or aziridine curing agent, wherein the resin soluble in the aromatic hydrocarbon solvent is an acrylic copolymer curable by the curing agent. The thermosensitive magnetic recording medium according to claim 1, which is characterized in that. 3. The thermosensitive magnetic recording medium according to claim 1, wherein the concealing layer contains aluminum powder.